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Structure and properties of lipase activated by cellulose-silica polyethersulfone membrane for production of pentyl valerate

Elias N, Wahab RA, Chandren S, Jamalis J, Mahat NA, Jye LW

Carbohydr Polym, 2020 Oct 01;245:116549.
PMID: 32718641 DOI: 10.1016/j.carbpol.2020.116549

Herein, this study extracted nanocrystalline cellulose (NC) and silica (SiO2) from raw oil palm leaves (OPL), and employed as nanofillers in polyethersulfone (PES) to produce NC-SiO2-PES as support to immobilize Candida rugosa lipase (CRL) (NC-SiO2-PES/CRL). XRD, TGA-DTG and FTIR-ATR data affirmed that NC and SiO2 were isolated from OPL with corresponding crystallinity indices of 68 % and 70 %. A 0.02 cm membrane size with 5% (w/v) of NC-SiO2 without PVP K30 was optimal for membrane fabrication. CRL immobilized on the Glut-AP-NC-SiO2-PES membrane gave a higher conversion of pentyl valerate (PeVa) (91.3 %, p < 0.05) compared to Glut-NC-SiO2-PES (73.9 %) (p < 0.05). Characterization of the NC-SiO2-PES/CRL biocatalyst verified the presence of CRL. Hence, raw OPL is a proven good source of NC and SiO2, as reinforcement nanofillers in PES. The overall findings envisage the promising use of NC-SiO2-PES/CRL to catalyze an expedient and high yield of PeVa, alongside the suitability of NC-SiO2-PES for activating other enzymes.
Effect of operative variables and kinetic study of butyl butyrate synthesis by Candida rugosa lipase activated by chitosan-reinforced nanocellulose derived from raw oil palm leaves

Elias N, Wahab RA, Chandren S, Abdul Razak FI, Jamalis J

Enzyme Microb Technol, 2019 Nov;130:109367.
PMID: 31421729 DOI: 10.1016/j.enzmictec.2019.109367

Currently, the chemically-assisted esterification to manufacture butyl butyrate employs corrosive homogeneous acid catalyst and liberates enormous quantities of hazardous by-products which complicate downstream treatment processes. This study aimed to identify the optimized esterification conditions, and the kinetic aspects of the enzyme-assisted synthesis of butyl butyrate using immobilized Candida rugosa lipase activated by chitosan-reinforced nanocellulose derived from raw oil palm leaves (CRL/CS-NC). The best process variables that gave the maximum conversion degree of butyl butyrate by CRL/CS-NC (90.2%) in just 3 h, as compared to free CRL (62.9%) are as follows: 50 °C, 1:2 M ratio of acid/alcohol, stirring rate of 200 rpm and a 3 mg/mL enzyme load. The enzymatic esterification followed the ping pong bi-bi mechanism with substrate inhibition, revealing a ˜1.1-fold higher Ki for CRL/CS-NC (55.55 mM) over free CRL (50.68 mM). This indicated that CRL/CS-NC was less inhibited by the substrates. Butanol was preferred over butyric acid as reflected by the higher apparent Michaelis-Menten constant of CRL/CS-NC for butanol (137 mM) than butyric acid (142.7 mM). Thus, the kinetics data conclusively showed that CRL/CS-NC (Vmax 0.48 mM min-1, Keff 0.07 min-1 mM-1) was catalytically more efficient than free CRL (Vmax 0.35 mM min-1, Keff 0.06 min-1 mM-1).
Induction of labour from 39 weeks in low-risk multiparas with ripe cervixes: A randomised controlled trial

Tan PC, Othman A, Win ST, Hong JGS, Elias N, Omar SZ

Aust N Z J Obstet Gynaecol, 2021 Jun 05.
PMID: 34089525 DOI: 10.1111/ajo.13377

BACKGROUND: Induction of labour (IOL) in low-risk nulliparas at 39 weeks reduces caesarean delivery. Multiparas with ripe cervixes typically have vaginal delivery within eight hours. Delivery at night and weekend are associated with higher maternal and neonatal mortality.
AIMS: To evaluate IOL in full-term multiparas with ripe cervixes to achieve delivery at normal working hours and improve maternal satisfaction.
METHODS: A randomised trial was performed in a tertiary hospital in Malaysia. Low-risk multiparas with ripe cervixes (Bishop score ≥6) were recruited at 38+4 -40+0 weeks, then randomised to planned labour induction at 39+0 weeks or expectant care. Primary outcomes were delivery during 'normal working hours' 09:00-17:00 hours, Monday-Friday and patient satisfaction by visual numerical rating scale.
RESULTS: For IOL (n = 80) vs expectant care (n = 80) arms respectively, primary outcomes of delivery at normal working hours was 27/80 (34%) vs 29/78 (37%), relative risk (RR) 0.9, 95% CI 0.5-1.7, P = 0.41, patient satisfaction was 8.0 ± 1.8 vs 7.8 ± 1.6, P = 0.41; presentation for spontaneous labour or rupture of membranes were 27/80 (34%) vs 70/79 (89%), RR 0.4, 95% CI 0.3-0.5, P
Characterization, optimization and stability studies on Candida rugosa lipase supported on nanocellulose reinforced chitosan prepared from oil palm biomass

Elias N, Chandren S, Razak FIA, Jamalis J, Widodo N, Wahab RA

Int J Biol Macromol, 2018 Jul 15;114:306-316.
PMID: 29578010 DOI: 10.1016/j.ijbiomac.2018.03.095

The contribution of chitosan/nanocellulose (CS-NC) to the enzymatic activity of Candida rugosa lipase covalently bound on the surface of CS-NC (CRL/CS-NC) was investigated. Cellulosic material from oil palm frond leaves (OPFL) were bleached, alkaline treated and acid hydrolyzed to obtain the purified NC and used as nano-fillers in CS. XRD, Raman spectroscopy and optical fluorescence microscopic analyses revealed existence of strong hydrogen bonds between CS and the NC nanofillers. The CRLs were successfully conjugated to the surface of the CS-NC supports via imine bonds that occurred through a Schiff's based mechanism. Process parameters for the immobilization of CRL were assessed for factors temperature, concentration of glutaraldehyde and pH, to afford the highest enzyme activity to achieve maximum conversion of butyl butyrate within 3h of incubation. Conversion as high as 88% was reached under an optimized condition of 25°C, 0.3% glutaraldehyde concentration and buffer at pH7. Thermal stability of CRL/CS-NCs was 1.5-fold greater than that of free CRL, with biocatalysts reusability for up to 8 successive esterification cycles. This research provides a promising approach for expanding the use of NC from OPFL for enhancing enzyme activity in favour of an alternative eco-friendly means to synthesize butyl butyrate.
Structure and properties of oil palm-based nanocellulose reinforced chitosan nanocomposite for efficient synthesis of butyl butyrate

Elias N, Chandren S, Attan N, Mahat NA, Razak FIA, Jamalis J, et al.

Carbohydr Polym, 2017 Nov 15;176:281-292.
PMID: 28927609 DOI: 10.1016/j.carbpol.2017.08.097

In this study, nanocellulose (NC) was successfully extracted from oil palm frond leaves (OPFL) using a combination of bleaching, alkaline treatment and acid hydrolysis. X-ray diffractogram revealed the extracted NC was crystalline with a crystallinity index of 70.2%. This indicates its suitability as nano-fillers for preparing the chitosan/nanocellulose (CS-NC) supports to immobilize Candida rugosa lipase (CRL) to produce the CRL/CS-NC biocatalysts. FTIR, FESEM and TGA characterizations of the CRL/CS-NC confirm the CRLs were successfully conjugated to the CS-NC supports. The air-dried CS-NC supports gave satisfactory immobilization of the CRLs (5.2mg/g) with the resultant CRL/CS-NCs catalysed conversions of ≥80% of butyl butyrate within 6h. Time course reaction profile revealed that 76.3% butyl butyrate conversion was achieved at 4h immobilization time using 3mg/mL of CRL/CS-NCs. NMR analyses on the purified butyl butyrate confirmed that the ester was successfully synthesized.
Clinicopathological correlation of oral candidiasis - Our experience in a tertiary centre over two decades

Tan CC, Lim D, Mohd Hisham NQ, Elias NA, Azli AS, Goh YC

Malays J Pathol, 2023 Aug;45(2):237-246.
PMID: 37658533

INTRODUCTION: Oral candidiasis is one of the most common fungal infections that has been widely reported around the world. In Malaysia, the available studies for this infection are scarce.
MATERIALS AND METHODS: This is a 20-year retrospective study aimed to investigate the prevalence, demographic characteristics, clinical presentations, and the association of oral candidiasis with clinical parameters in oral candidiasis cases reported in the Faculty of Dentistry, Universiti Malaya from 1999 until 2019. A total of 12,964 histopathological records from the Oral Pathology Diagnostic and Research Laboratory (OPDRL) between 1999 to 2019 were retrieved. Oral candidiasis cases were selected according to the inclusion and exclusion criteria. Information of interest was obtained and analysed.
RESULTS: From the total records retrieved, 378 oral candidiasis cases were recorded and 82.8% were diagnosed from smear test. This study showed that oral candidiasis was predominantly reported in female (64.2%) and Indian population (64.2%). The peak incidence was in the sixth decades of life (27.0%). The most commonly affected site was tongue and coated tongue was the most common clinical presentation. More than 50% of the cases had comorbidity and 10.6% were associated with dentures. Ethnicity and site of occurrence were significantly associated (p<0.05) with oral candidiasis.
CONCLUSION: This is the first large-scale study of oral candidiasis cases in Malaysia. The findings of this study are useful for clinical assessment of patients suspected of oral candidiasis.
Fulltext Electrospun Magnetic Nanocellulose-Polyethersulfone-Conjugated Aspergillus oryzae Lipase for Synthesis of Ethyl Valerate

Hussin NH, Wahab RA, Elias N, Jacob AG, Zainal-Abidin MH, Abdullah F, et al.

Membranes (Basel), 2021 Dec 09;11(12).
PMID: 34940473 DOI: 10.3390/membranes11120972

A novel greener MNC/PES membrane was developed through an electrospinning technique for lipase immobilization to catalyze the synthesis of ethyl valerate (EV). In this study, the covalent immobilization of Aspergillus oryzae lipase (AOL) onto an electrospun nanofibrous membrane consisting of magnetic nanocellulose (MNC) and polyethersulfone (PES) to produce EV was statistically optimized. Raman spectroscopy, Fourier-transform infrared spectroscopy: attenuated total reflection, field emission scanning electron microscopy, energy dispersive X-ray spectroscopy, thermal gravimetric analysis (TGA), and differential thermal gravimetric (DTG) of MNC/PES-AOL demonstrated that AOL was successfully immobilized onto the fibers. The Taguchi design-assisted immobilization of AOL onto MNC/PES fibers identified that 1.10 mg/mL protein loading, 4 mL reaction volume, 250 rpm stirring rate, and 50 °C were optimal to yield 72.09% of EV in 24 h. The thermal stability of MNC/PES-AOL was improved by ≈20% over the free AOL, with reusability for up to five consecutive esterification cycles while demonstrating an exceptional half-life of 120 h. Briefly, the electrospun MNC/PES fibers that immobilized AOL showed promising applicability in yielding relatively good EV levels. This study suggests that using MNC as fillers in a PES to improve AOL activity and durability for a longer catalytic process could be a viable option.